BRUSSELS—European Union regulators are preparing to open a formal investigation into corporate-tax regimes in Ireland, Luxembourg and the Netherlands on Wednesday, according to a person familiar with the matter, amid concerns that multinational companies such as
Apple Inc.
AAPL -1.94%
enjoy sweeter tax deals than are permitted under EU law.

It is part of a broader crackdown on tax evasion and tax avoidance agreed to by EU leaders in the wake of the region's financial crisis, aimed at boosting national budgets and soothing voter anger over cuts to welfare programs.

The commission will announce a formal investigation into tax deals granted to multinationals at a news conference on Wednesday, the person familiar with the matter said Tuesday. The probe is likely to consider whether generous corporate-tax regimes in Ireland, Luxembourg and the Netherlands amount to illegal state aid.

If the commission's investigation establishes that companies received state aid, it could require that they pay it back. But in practice, such demands are uncommon.

The commission said in September it had started gathering information about tax deals offered to multinationals in Ireland, the Netherlands and Luxembourg. "We are collecting information on the subject," EU spokesman Antoine Colombani said at the time. He said more countries also could come under scrutiny.

An EU spokesman didn't respond to repeated requests for comment on Tuesday night.

U.S. Senate investigators last year found that Apple paid little or no corporate tax on at least $74 billion in revenue over the previous four years, largely by exploiting a loophole in Ireland's tax code.

Apple has denied that its tax arrangements are designed to avoid taxes, and said it pays all taxes due and creates hundreds of thousands of jobs. It wasn't clear which companies' tax arrangements might be examined in the probe.

The EU's tax commissioner,
Algirdas Semeta,
has warned that the region "can no longer afford freeloaders who reap huge profits in the EU without contributing to the public purse."

The Irish Finance Ministry declined to comment late Tuesday. The Dutch and Luxembourg governments couldn't immediately be reached.

The U.S. investigation found no evidence that Apple did anything illegal. And the Irish government last year denied it helps shelter some of the world's largest corporations from paying taxes, saying its long-standing low corporate-tax regime is transparent and doesn't make it a tax haven.

It insists that much of the criticism is unfair and has denied it had negotiated "any fancy" treatments with Apple or any other company. It says that it doesn't, and regardless can't under current international rules, tax the many billions of dollars that companies like Apple funnel through Ireland-based companies to other overseas subsidiaries.

Google, Amazon and Starbucks have been questioned by the U.K. Parliament's Public Affairs Committee to explain their tax arrangements.

Starbucks said in April it would move its European corporate headquarters to London from the Netherlands and pay more taxes in the U.K.

Through its competitive tax rate, Ireland has attracted large amounts of investments and jobs from U.S. and other international companies. Ireland is still struggling to recover from the property and banking crash that struck in 2008, and those international investments made over many years have helped soften the economic effects of the crisis.

U.S. companies have used the country as a base for production aimed at European and international markets for many decades. The American Chamber of Commerce in Ireland has estimated that U.S.-owned companies in Ireland produced goods and services worth over $55 billion and says that U.S. companies are so prevalent that Ireland is strategically important to "corporate America."

However, in a sign of Irish concerns about potential reputational damage following the U.S. Senate revelations, the government last year decided to close a loophole between Irish and U.S. tax codes used that effectively meant that a small number of companies, including Apple, could shift revenue into Ireland and out to other centers that rendered the revenue "stateless" or free of tax anywhere in the world. Ireland's government has said that such aggressive tax planning is unacceptable.

It has also welcomed and says it has little to fear from any multilateral changes that may arise after the Group of Eight major economies last summer committed itself to examine and reform global taxation systems and curtail the use by giant companies of tax havens.

In 2011, Irish Prime Minister Enda Kenny clashed with former French President
Nicolas Sarkozy,
who wanted Dublin to raise the country's corporation tax rate in return for the country getting more favorable bailout terms. The Irish government has insisted that effective tax rates applied in France were lower than those levied in Ireland.